Small receiver



April 27, 1937. T. KATO 2,078,385

SMALL RECEIVER F1}. 6 Filed June 7. 1954 FD,

"II'IJ a WIIIIIIA 'lllll lpu Patented Apr. 27, 1937 SMALL RECEIVER Tooru Kato, Osaka, Japan Application June "I, 1934, Serial No. 729,485 In Japan June 13, 1933 3 Claims.

This invention relates to the small receiver of the magnetic type which consists of a permanent magnet, soft iron pole pieces, a diaphragm and an exciting winding.

The object of invention is to provide an improved small and light receiver which is suitable for-inconspicuous wear, and operative with high efllciency.

The invention is illustrated on the drawing and hereinafter more fully described.

On the drawing:

Fig. 1 is a plan view or the small receiver.

Fig. 2 is a vertical section upon the line AB of Fig. 1.

Fig. 3 is a vertical section oil a substitutive secondary short pipe.

Fig. 4 is a vertical section of the other substitutive secondary short pipe.

Fig. 5 is a plan view of a permanent magnet and an iron core.

Fig. 6 is a perspective view of Fig. 5.

Fig. 7 is a plan view of outer pole piece.

i is a soft iron core surrounded by a winding 2 which is supplied with voice current in any convenient way. One end of the core becomes a single pole 3, the other is riveted to a permanent magnet which has three magnetic branches 4, t and 4". All branches are bended symmetricallyj upwards and those ends form three poles 5, 5'! and 5".

6; is a soft iron plate having low magnetic reluctance and small residual magnetism. It is screwed on the ends of three poles, and so becomes outer pole piece. The plate has a round opening 1 in the center where appears the end of a single pole 3 surrounded by an air gap of equal width. The plate has also three slots 8, 8' and 8" which run from the opening radially towards the circumference of the plate 6, passing midway between the three poles.

9 is a diaphragm made of any suitable elastic nonmagnetic metal such as light alloy. A magnetic-iron plate ill of small diameter is fastened to the center of the diaphragm 9 by a paste ll of organic material and they are set on the plate 6 by a ring I! made of the same material as the' diaphragm.

I3 is a resonant cup which is fixed to the magnet box l5 by the inside of the body l4. I6 is a ring of nonmagnetic material which is located between the inside top of the resonant cup [3 and the diaphragm 9 making a resonant chamber ll. I8 is a short pipe, the outside of which is fixed to the opening at the top of the resonant cup. I9 is a secondary short pipe, the outside of which is fixed to the inside of the short pipe. The guard 20 of the secondary short pipe is seated upon the top of the short pipe. l9 and I9" are substitutive secondary short pipes. The diameters of these secondary short pipes are different from each other.

2| is an ear piece to be inserted into the ear hole and is screwed outside the short pipe l8.

As above mentioned, the magnetic circuit is constructed from the soft iron core forming the magnetic axis I, single pole 3, three or more magnetic branches 4, 4 and 4", three or more poles 5, 5' and 5", and outer pole piece which is screwed to the poles. The function of the outer pole piece which is provided with the opening and radiating slots is to concentrate the magnetic force uniformly around the air gap, and produce uniform attractive force on the diaphragm. Thus the result is to so lessen the concentration of the magnetic force in one or two parts of the magnetic plate, that the magnetic force will pass into the center of the diaphragm, vibrates it normally, and thus magnifies the sound in the sound producer in its original tone and also makes it audible asclearly as possible.

Such circuit is not only different from any known type in that it is well balanced at the center of the magnetic axis and that the loss of magnetic force is greatly decreased but also different from ordinary Sell typein that the magnet does not attract merely one part of the diaphragm. Moreover as only the flux which closes the small air gap between the round opening and the single pole acts upon the magnetic plate, so the diaphragm vibrates smoothly and accurately corresponding to the supplied voice current which passes through the exciting winding.

The attractive plate is adhered to the center of the diaphragm by a paste of organic material, so that such bad physical effects to the diaphragm are eliminated as by other adherent means like soldering, riveting, welding, embracing and electric casting.

Speaking in detail, soldering riveting, welding, embracing and electric casting have all unavoidable mechanical defects which cause strained vibration. Namely, in soldering, the thickness of soldering on the vibrating diaphragm can not be made uniform. In riveting, the diaphragm itself causes strain while working up. In welding, the hardness of the diaphragm can not be made uniform. In embracing, the diaphragm is rumpled. Lastly in electric casting, it takes a long time to cast an attractive plate of considerable thickness and also some operation is 2 amass necessary to work upon the surface of the plate, during which the diaphragm is apt to be rumpled. On the contrary, in the present application. the attractive plate is fastened to the s diaphragm by an organic paste, so that the diaphragm is neither strained nor rumpled, and working up is very easy. The fact that the diaphragm and the attractive plate are fastened to each other through the thick film of organic 10 paste, is much more effective to reproduce sounds as clearly asnaked voices than that which is done by other means of fastening the plate directly to the diaphragm. Moreover, as organic paste itself is non-magnetic material, even if 15 thickness of the paste itself become unequal and unbalanced, vibrations are not particularly strained. These characteristics can only be attained by using organic paste.

Lastly, the musical scale may be properly ad- 20 iusted by using the pipe of suitable diameter. For instance. in the case of a person whose defect oi. hearing is found at low-pitch sound, the

pipe of small diameter should be used, while in the case of a person whose defect-of hearing is 25 found at the high-pitch sound, that of large diameter should be used.

A distinctive feature of the invention is the complete small receiver consisting of the improved magnetic circuit apparatus, improved so vibrating apparatus, and the pipe of suitable diameter for defect of hearing. The disagreeable eifect common to the ordinary receiver by reason of the small size of magnet, diaphragm, resonant chamber etc. may be largely eliminated and the sound may be smoothly reproduced, magnified, and adjusted so suitably that the defect of hearing can be removed.

I claim:

1. A small receiver having a portion to be inserted into an ear hole and comprising a resonant cup having an opening in its top and a pipe mounted within the opening, and a plurality of secondary pipes having diiferent internal diameters to be selectively placed one at a time within said first mentioned pipe so that the defect at any pitch of hearing can be treated. 2. A device according to claim 1 in which said secondary pipes are provided with an upper flange to rest upon the upper rim of the first mentioned 9 D 3. A small receiver having a portion to beinserted in the ear comprising a resonant cup having an opening in its top and a plurality of interchangeable pipes of diiferent internal diameters, said cup being constructed to receive said pipes one at a time in the opening in said cup so that the defect at any pitch of hearing can lie treated.

IOORU KATO. 

